Multi-user multiple-input multiple-output (MU-MIMO) systems with a large number of base station antennas provide high throughput communications for emerging wireless deployments. By spatially multiplexing signals, a base station antenna array may serve many separate user terminals using the same time-frequency resource. This spatial resource sharing policy may serve as an alternative to costly spectrum licensing and avoid the costly procurement of additional base stations.
Although the benefits of spatial multiplexing may be fully realized when the number of base station antennas is equal to the number of scheduled user terminals, MU-MIMO systems with an excessively large number of antennas, also known as “Massive MIMO” may also provide additional benefits. Massive MIMO can increase the system's capacity while simultaneously improving the radiated energy efficiency via energy focusing. Massive MIMO systems can also be integrated with inexpensive, lower power components.
Unfortunately, massive MIMO implementations present some very challenging engineering aspects, including, e.g., antenna design, pilot contamination, inter-cell interference management, and hardware impairments. Additionally, the computational burden required to determine precoding matrices that compensate for variations in channel conditions may often be unreasonable. This is particularly true in dynamic environments where pilot signal calibrations must be frequently performed as channel conditions change. There exists a need for systems and methods to facilitate efficient channel recalibration despite these substantial computational burdens.
While the flow and sequence diagrams presented herein show an organization designed to make them more comprehensible by a human reader, those skilled in the art will appreciate that actual data structures used to store this information may differ from what is shown, in that they, for example, may be organized in a different manner; may contain more or less information than shown; may be compressed and/or encrypted; etc.
The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed embodiments. Further, the drawings have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be expanded or reduced to help improve the understanding of the embodiments. Similarly, some components and/or operations may be separated into different blocks or combined into a single block for the purposes of discussion of some of the embodiments. Moreover, while the various embodiments are amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the particular embodiments described. On the contrary, the embodiments are intended to cover all modifications, equivalents, and alternatives falling within the scope of the disclosed embodiments as defined by the appended claims.